Travel Time Reliability Reference Manual/Data Storage
Data Storage
editDue to the large size of the NPMRDS data sets, it is not possible to open the CSV files containing travel time data in Microsoft Excel. While Microsoft Access provides the ability to handle slightly larger data sets, MS Access is also limited in the amount of data it can hold (typically around 2 GB). With each month of data containing between 500 MB and 4 GB, depending on the region, it is recommended to use a non file-based relational database. MySQL and PostgreSQL are examples of open source databases which can handle these large data sets.
The data is often stored as two tables, one which holds the static TMC information and the other which holds the speed/travel time data. The two tables can be joined by the TMC id/name which is parameter in both data sets. Details of each data set can be found on the NPMRDS data format page.